The fight is sharply drawn. In an op-ed in The Washington Post, Perry warned of a growing "isolationism" in the country, singling out Paul as "curiously blind" to growing threats in Iraq. Perry also reminded voters that he had served in the military and governed a large state, two achievements that Paul, who was first elected to the Senate in 2012, can't claim.
Paul took the incoming and quickly tossed it back in a piece published in Politico on Monday under the headline "Rick Perry Is Dead Wrong."
Taking a swipe at Perry's new smart-man glasses, he said the eyewear didn't allow the governor to see the world any more clearly. He pointed out that Perry believed, even before the recent victories by Sunni insurgents, that the United States should send more troops into Iraq. Wondering pointedly how Perry found the time to go after him, what with 60,000 undocumented immigrant children on his border, Paul said that to call him an isolationist was to tar the whole country with the same brush. Like him, an overwhelming majority of Americans don't want Americans to die for the Iraqis who "dropped their weapons, shed their uniforms and hid" at the first sign of trouble, he wrote.
They have reason to go at it. As potential candidates, both have to seize the momentum away from noisier potential competitors such as New Jersey Gov. Chris Christie and Sen. Ted Cruz of Texas. The usual way for a Republican to stand out is to grab at shiny electoral objects such as taxes, guns, gay marriage, abortion and rejection of anything involving President Barack Obama.
But their war of words is bigger than that and the both of them. They've begun a conversation the Republican Party has to have over a Republican president's decision to take the country into a ruinous war over the lie that Saddam Hussein had weapons of mass destruction. At a Politico event Monday, former Vice President Dick Cheney, who doesn't have to run again, unequivocally defended the 2003 invasion that ended up costing almost 4,500 American lives and left Iraq violently ungovernable. Cheney wouldn't say whether Paul would be a dangerous president, but he said "isolationism is crazy" and that anyone who thinks we can retreat behind our oceans "is out to lunch."
For now, Paul and Perry are the proxies in the war for the foreign-policy soul of the party between the neo-isolationist/tea party/libertarians and the strong-on-defense establishment types. When Megyn Kelly of Fox News tells Cheney that "history has proven that you got it wrong," you know Republicans are no longer knee-jerk hawks.
Wading into this briar patch is perfect for Perry and Paul. Both need to prove they're broader than their current resumes suggest. As governor, all Perry had to do was keep Texas safe from an invasion by Mexico. As a senator, all Paul has to do is run his mouth.
The three-term Texas governor's 2012 presidential run was supposed to blow everyone away, but he peaked in the polls on the hot August day he announced his candidacy. He missed every opportunity to shine in the debates and became a reference point for senior moments when he failed to remember the third Cabinet department he was set on abolishing.
As for Paul, he needs to show that he's more than just a first-term tea party-supported senator. He also needs to prove he's not a niche player like his father, former Rep. Ron Paul, who helped get him to the party but will keep him from being the life of it. Dad wasn't just an isolationist but a fringe character who had no trouble reciting the institutions he would abolish, from the Pentagon to the Federal Reserve.
Rand Paul has looked a bit bumbling himself by questioning the wisdom of the Civil Rights Act. He also seems too dependent on his father's network, and a little kooky by authoring a bill to legalize interstate traffic in unpasteurized milk and putting forward a doomsday budget. He also proposed the Read the Bills Act and the One Subject at a Time Act.
Nonetheless, he broke out of the pack, winning grudging respect and inciting some fear when he found a good cause in the ill-defined use of military drones. His filibuster on the subject forced the Justice Department to clarify when, where and against whom they could be deployed.
Perry is working hard at a second chance to make a first impression. After deciding not to run for a fourth term, he formed a nonprofit that allowed him to take fact-finding trips to Europe, Israel and Iowa. He checks off a lot of the activist Republican boxes: He's a gun nut (he has his own concealed-carry permit and an A+ NRA rating); he loves the death penalty; and he opposes abortion, gay marriage, taxes and Obamacare. He's been super-successful at bringing companies to Texas.
He has made himself vulnerable on immigration, however, by displaying a soft spot for the Dream Act. Come 2016, that might not be such a liability. Surprisingly, Rand Paul himself has a softer take on immigration than his party, part of his recent call for Republicans to build a bigger tent.
Before this year, Perry and Paul looked like fringe candidates (Sen. John McCain famously called Paul a "wacko bird.") Both have upped their games, and Paul is a force his party fears. If nothing else, the two are going to drag the party into a reckoning over Iraq that's long overdue. Better to have it now than in 2016.
(Margaret Carlson is a Bloomberg View columnist.)